In recent years, a backlight that is used for a liquid crystal display device and the like is required to have higher brightness so as to further improve the visibility of a display screen.
However, in a pattern shape of current connection wirings formed on a circuit substrate having an LED (Light Emitting Diode) as a light source mounted thereon, a distance between the LEDs to be mounted is limited, so that there is a limit on the number of the LEDs.
In the meantime, the known references relating to this disclosure is JP-A-2004-233809 and JP-A-2006-237320, for example.
FIG. 5A is a plan view illustrating a light source unit of a side light-type backlight according to the background art and FIG. 5B is an enlarged plan view of an example of a substrate (circuit substrate having an LED mounted thereon) in the light source unit of the side light-type backlight according to the background art.
As shown in FIG. 5A, according to the side light-type backlight of the background art, a plurality of LEDs 101 mounted on a substrate 102 is arranged with contacting a side end face 103s of a light guide plate 103. The plurality of LEDs 101 illuminates the light from the side end face 103s of the light guide plate 103 to an inside thereof.
The substrate 102 on which the plurality of LEDs 101 is mounted is an FPC (Flexible Printed Circuit) and a face thereof is covered with an insulating coverlay 104, as shown in FIG. 5B. A land 102r, to which a pair of electrodes (not shown) of each LED 101 is respectively connected, is exposed from an opening 104k of the coverlay 104, including a part of a connection wiring (conduction wiring) connected to the land 102r. In other words, a part of the connection wiring connecting the opposed lands 102r of the adjacent LEDs 101 is covered by a part of the coverlay 104. On the substrate 102, a plurality of pairs of lands 102r, each pair of which corresponds to the pair of electrodes of each LED 101, is arranged at an interval of a pitch pt1 (refer to FIG. 5B).